The current purpose of this protocol is to evaluate the potential value of a long-acting calcium channel blocker (amlodipine) in the prevention of nephrotoxicity associated with the use of cyclosporin and tacrolimus after orthotopic liver transplantation in children. This project is designed to assess glomerular filtration rate before OLT and sequentially afterwards while receiving amlodipine as well as during a period when drug is washed out to determine whether the effects of immunosuppressants on the kidney can be prevented/reversed. During the study period, 10 new subjects were enrolled, and 3 are being followed after OLT.